1. Technical Field
The present invention relates to a method and apparatus for transmitting data (for example multi-media content) to a mobile device, especially via one or more Wireless Local Area Network (WLAN) Access Points (AP's) connected to a central wired network.
2. Related Art
The Institute of Electrical and Electronic Engineers (IEEE) has developed a series of standards all of which commence with 802.11 and which are commonly known collectively as the 802.11 standards (or more informally as the 802.11x standards). Technically, the IEEE consider that there is only the one 802.11 standard (which is often referred to as the legacy standard) and then there are multiple amendments to the standard (e.g. amendment 802.11g, 802.11a, 802.11b, 802.11n, 802.11i, etc.) although in practice several of these “amendments” (e.g. 802.11g, 802.11a, 802.11b and the not-yet finalised 802.11n) are typically viewed by persons skilled in the art as separate standards in their own right. These are the standards most commonly used to implement WLAN's and so the term WLAN is generally used to refer to a WLAN formed using 802.11 technology. Additionally, the term Wi-Fi (which is a registered trade mark of the Wi-Fi Alliance) is in common popular usage and designates WLAN products and services which have been certified by the Wi-Fi Alliance as operating in accordance with the 802.11 standards. Devices which operate according to any of these standards are known as WLAN-enabled devices (or, where applicable, as Wi-Fi enabled devices) and portable consumer devices are increasingly becoming WLAN enabled.
The WLAN connection enables a WLAN enabled mobile device to download (or upload) data at rates of up to 54 Mbits/s (for the 802.11a or 802.11g amendments to the 802.11 legacy standard—subsequent standards/amendments such as the 802.11n amendment will allow even greater maximum data rates) from an “access point” via a wireless transmission protocol. The access point is a (generally fixed) device which has a (normally) wired connection to a central network via an Internet Service Provider. The wired connection is generally through some sort of access network and is usually referred to as a backhaul connection. In many cases the backhaul will be via a Digital Subscriber Line (xDSL) connection such as an Asynchronous DSL (ADSL) connection. As more and more WLAN access points are set up, the use of WLAN (especially using the 802.11 standards) as a mechanism for delivering data to mobile devices becomes more and more attractive as a general proposition, either as the sole means of delivering the content or as an augmentation to data delivered via other means such as GPRS over a cellular network.